Fabric container running out of memory. JVM heap dump reveals byte array with a few hundred MB of git operations

Issue

One of our Fabric containers has run out of JVM heap memory (java.lang.OutOfMemoryError raised).
We took a JVM heap dump and analysis of this heap dump shows a large byte array spawning several hundred MB in size which seems to contain git operations.
This happens despite configuring the container to use gitGcOnLoad=true (See article 2203681 for details).

The byte array seems to contain millions of records of this type

64c8ca4b4e14e3dddd75880260d853de2149b 9f75a6ba4554a38925f75bd7dd243a0121ac tst6fuse <tst6fuse@test.redhat.org> 1477555254 +0100 checkout: moving from 64c8cba4b4e14e3ddddf758802604d853de2149b to 2.2
9f75a6ba42504a389a25f5bd7dd243da021ac 9f75a6a425504a389a25f75bd7d243da01ac tst6fuse <tst6fuse@test.redhat.org> 1477555256 +0100 checkout: moving from 2.2 to HEAD
9f75a6ba425504389a2f75bd7dd243da0121ac 9f75a6ba42504a389a25f75d7dd24a0121ac tst6fuse <tst6fuse@test.redhat.org> 1477555256 +0100    checkout: moving from 9f75a6ba425504a389a25f75bd7dd243da0121ac to 2.2
9f75a6ba425504a39a25f75bd7dd243d0121ac 9f75a6ba4550a39a25f7bddd2413da0121ac tst6fuse <tst6fuse@test.redhat.org> 1477555257 +0100    checkout: moving from 2.2 to HEAD